Question

7. Decide whether the DNA fragment shown below will be cut by the following restriction endonucleases: EcoRI (5’-GAATTC-3’), AluI (5’-AGCT-3’), PstI (5’-CTGCAG-3’). For each one that cuts, how many products will be produced?

5’-AAGAATTGCGGAATTCGAGCTTAAGGGCCGCGCCGAAGCTTTAAA-3’

3’-TTCTTAACGCCTTAAGCTCGAATTCCCGGCGCGGCTTCGAAATTT-5’

Answer 1

Restriction endonuclease
Restriction endonuclease, is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. A protein produced by bacteria that cleaves DNA at specific sites along the molecule. In the bacterial cell, restriction enzymes cleave foreign DNA, thus eliminating infecting organisms.These enzymes are found in bacteria and archaea and provide a defence mechanism against invading viruses specially by cleaving viral genome .
Eukaryotic cells do not have restriction endonucleases. This is because the DNA of eukaryotes is highly methylated.
Restriction enzymes recognise specific short DNA sequences and carry out the endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates.


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